10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The CO-MP exam has 120 questions and runs 4 hours 30 minutes.
These 10 free CO-MP questions are organized by exam domain, so you can see how each part of the Colorado Master Plumber License Exam blueprint is tested. Reveal the answer and explanation under each question.
A fertilizer-injection unit is hard-piped to a potable irrigation supply. Its booster pump can produce 95 psi while the supply is at 60 psi. The chemical mixture is a health hazard, and the design calls for a listed mechanical backflow assembly rather than an air-gap break tank. Which assembly protects against the hazard and the possible reversal mechanism?
Correct answer: A - Reduced-pressure principle assembly, ASSE 1013.
Two bathroom groups on the same floor use a correctly sized horizontal wet vent. The drainage sequence runs from the dry-vented lavatory connections through the bathtub and water-closet connections to junction J, the downstream end of the wet-vented section. A separately trapped and vented laundry standpipe is being added. Where may its drain join without disqualifying the bathroom wet vent under the 2021 IPC?
Correct answer: C - Downstream of junction J, after the wet-vented section.
A lodging renovation supplies several showers through a central valve listed only to ASSE 1017. Each shower still has an ordinary two-handle faucet. Users experience abrupt temperature changes when nearby fixtures open, even though the central mixing valve works as designed. The fixture-level protection required by the 2021 IPC is:
Correct answer: C - An individual ASSE 1016 automatic compensating valve installed at every shower.
Before concealment, new PEX water-distribution piping must be tested for a system working pressure of 70 psi. All proposed test pressures are within the component ratings. Which procedure satisfies the 2021 IPC test requirements?
Correct answer: A - A water test maintained at 80 psi for 20 minutes without leakage.
After a mechanical room has been unused for several months, sewer odor is traced to a dry floor-drain trap. Refilling the intact trap stops the odor. The vent is clear, and discharging nearby fixtures does not disturb the restored seal. The owner wants evaporation protection without adding a potable-water primer connection. Which installation is permitted by the 2021 IPC?
Correct answer: A - Retain the P-trap and add a listed ASSE 1072 barrier-type trap-seal protection device.
A roof-drain submittal covers 2,400 square feet of horizontal roof projection. One 800-square-foot vertical wall drains rainwater onto that roof. The specified 100-year, 1-hour rainfall intensity is 4 inches per hour, and water head at the drain may not exceed 2 inches. Four drain options are rated at that head. Using Q = 0.0104 × rainfall intensity × effective drainage area, with Q in gpm, which is the smallest adequate rating?
Correct answer: C - 130 gpm
A new building has basement fixtures on a finished floor at elevation 98.0 ft and ground-floor fixtures at elevation 109.0 ft. The next upstream public-sewer manhole cover is at elevation 102.4 ft. Both groups can drain by gravity, and their branches join before leaving the building. Select the backwater-valve arrangement that complies with the 2021 IPC.
Correct answer: D - Protect only the basement branch, upstream of the junction.
A coordination check of a 4-inch building drain records four details below. Which detail requires correction under the 2021 IPC?
Correct answer: D - A fixed cabinet leaves 14 inches of working clearance in front of a cleanout opening.
A straight pipe spool will connect two parallel horizontal runs through a pair of 45-degree fittings. The centerlines are displaced 6 inches sideways and 8 inches vertically; both displacements are perpendicular to the original direction of the runs. Use a net fitting allowance of 1.25 inches at each end, including joint engagement. What cut length is needed, to the nearest tenth of an inch?
Correct answer: B - 11.6 inches
A pressure logger on a home's cold-water piping records 58 psi with the storage water heater off. With all fixtures closed, pressure climbs gradually to 112 psi during a heating cycle, then returns to 58 psi when a faucet is briefly opened. Utility-side pressure stays steady, and the rise does not occur with the heater off. A service backflow assembly was recently installed; there is no expansion-control device. Which correction addresses the cause?
Correct answer: A - Install a correctly sized expansion tank on the cold-water line between the backflow assembly and heater.
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